The present invention relates to suspension assemblies used in rotary disk storage devices such as magnetic disk devices or the like and, more particularly, to a suspension assembly exhibiting excellent performance in a track follow-up ability, an impact resistance, and a load/unload operation.
In a magnetic disk device, a rotary magnetic disk as a recording medium rotates at a high speed and a head moves across a surface of the magnetic disk in a floating position with respect thereto for reading and writing data. The head is mounted on a slider and the slider is supported by a suspension assembly. The suspension assembly, supported by an actuator mechanism, is arranged so as to be movable in a substantially radial direction of the magnetic disk. When the magnetic disk rotates at a high speed, a viscous air flow generated on the surface of the magnetic disk flows between an air bearing surface (ABS) formed on a bottom surface of the slider and the surface of the magnetic disk to form an air bearing. This gives the slider an ascending force and the slider, as a result, floats above the disk by retaining a slight gap therefrom.
FIG. 1 shows a schematic view of a common head suspension assembly 5. The head suspension assembly 5 is formed as a multi-piece type suspension assembly comprising a mount plate 2, a load beam 4, a hinge 13, a flexure 6, and a wiring layer 8. A slider 9 is attached to a side, facing a disk, of the flexure 6. The slider 9 is provided with a head (not shown) for reading and writing data. The head suspension assembly 5 is mounted to an actuator arm forming part of an actuator mechanism by the mount plate 2. The hinge 13 performs a function of adjusting a load and stiffness of the load beam 4 by separating the load from the stiffness.
The wiring layer 8 is connected to a head having one end which is attached to the slider 9. The wiring layer 8 is laminated on the surface of a metal layer of the flexure 6 by a photolithographic etching process, the wiring layer 8 being formed as a stack of layers including a dielectric material layer, a conductive material layer, and a protective layer. The wiring layer 8 is further provided with an area separated from the metal layer and extending aerially.
The load beam 4 brings the slider to a position near a predetermined track in accordance with the operation of the actuator mechanism. In addition, the load beam 4 generates a negative pressure for pressing the slider down against the surface of the magnetic disk. The slider 9 maintains a predetermined distance from, and thus floats above, the surface of the magnetic disk by balancing the ascending force received from the air bearing acting as a positive pressure against the negative pressure created by the load beam 4.
FIG. 2 is a plan view of the flexure 6 shown in FIG. 1 as viewed from the disk side. The flexure 6 is formed of a thin stainless steel metal layer overall. A supporting area 18 has a portion serving as a weld spot 20 that is spot-welded to the side of a supporting end of the load beam 4. A pair of arms 10a, 10b extends from the supporting area 18 toward a leading end of the load beam 4 and is joined together at a leading end area 16. In addition, the flexure 6 includes a flexure tongue 12 formed in such a manner as to be supported by the leading end area 16 and the arms 10a, 10b. 
A dimple contact point, or a DCP, is defined at substantially a center of the flexure tongue 12. The slider 9 (not shown) is bonded to the flexure tongue 12 so that the DCP is substantially centered on the slider 9. Further, wiring layers 11a, 11b are laminated on the metal layer. The wiring layers 11a, 11b depart from the metal layer at an end portion of the supporting area 18 and are terminated so as to align with the position of a bonding pad provided in the slider 9. A limiter 14 is formed on the side of the actuator arm of the flexure tongue 12.
FIG. 3 shows a schematic construction of a side face of the flexure 6 shown in FIG. 2. The flexure tongue 12 is supported by a cantilever structure formed by the supporting area 18 of the metal layer welded to the load beam 4 at the weld spot 20 and the two arms 10a, 10b. A dimple 7 is formed in the load beam 6 by a stamping operation. The dimple 7 comes in contact with a substantial center portion on the bottom of a slider-mounting surface of the flexure tongue 12 to form the DCP. The slider 9 flexibly pivots about the dimple 7, floating on the air bearing formed on the magnetic disk to perform a follow-up movement.
A pivotal motion is generally known as a pitch and roll motion or a gimbal motion. An error can occur when the slider is aligned with the track due to various manufacturing errors occurring in different component parts making up the magnetic disk device or irregularity in behavior of the air bearing or the suspension assembly. The slider, however, makes the pivotal motion to cause a slight pitching motion or rolling motion, thereby maintaining the air bearing and thus compensating for the error.
The rolling motion is that which occurs when, as shown in FIG. 1, the slider that is positioned so that the air bearing surface forms a predetermined angle with respect to the disk surface makes a pivotal motion about an X-axis, which is a longitudinal direction of the suspension assembly. Meanwhile, the pitching motion is a pivotal motion made by the slider about a Y-axis included in a plane perpendicular to the X-axis and parallel with the disk surface. Characteristics of the pitching motion and the rolling motion are determined by an entire structure of the suspension assembly. The following nonetheless holds true: the smaller pitch stiffness and roll stiffness of the flexure tongue, the better the track follow-up ability, thus realizing a better compensation motion.